Fluid pressure relief valves



Sept. 15, 1959 F. G. FREEMAN 2,904,066

FLUID PRESSURE RELIEF VALVES Filed May 13, 1957 J g 7 I n ///P/ /7/fi77f 0 P1 7 .7121) tan/fol? F G.Fveezna,

United States Patent FLUID PRESSURE RELIEF VALVES Frank George Freeman, Solihull, England, assignor to Joseph Lucas (Industries) Limited, Birmingham, England Application May 13, 1957, Serial No. 658,564

Claims priority, application Great Britain May 16, 1956 1 Claim. (Cl. 137-493) If hydraulic or pneumatic systems for transmitting motive fluid from a pump to an apparatus to be actuated it is customary to provide a relief valve for enabling the fluid to escape and return to the pump or a sump when the pressure in the system exceeds a predetermined amount. When the system is required to deal with a large volume of motive fluid at high pressure a relief valve of conventional construction is found to be unsatisfactory and the object of the invention is to enable a relief valve to be provided in a form capable of dealing satisfactorily with high pressures and large volumes of fluid.

A valve in accordance with the invention comprises in combination a body part having therein a longitudinal bore and a pair of laterally arranged ports leading to the bore in the regions of its opposite ends respectively, a peripherally gapped hollow piston slidable in the bore to control communication between the ports, and provided with a central boss, the latter having therein a pair of coaxial bores extending inwardly from opposite ends of the boss, and a pair of passages whereby the inner ends of the said coaxial bores communicate respectively with the ports, springs acting on opposite ends of the piston to resist movement of the latter from a position in which it interrupts communication between the ports, and stationary plugs extending into and occupying parts of the bores in the boss so that fluid admitted under pressure to either of the ports has access through the associated passage in the piston to the corresponding bore in the boss, and tends to move the piston into a position for establishing communication between the ports.

In one example, as illustrated by the accompanying drawing, the body part a has therein a cylindrical bore which is closed at its ends by separately formed hollow cover pieces b, c, and at or adjacent to the ends of the bore are provided in one side of the body part an inlet port d and an outlet port e.

Within the bore is contained a hollow piston comprising a peripheral part and a central boss g of rather greater length than the peripheral part, and a radial web or webs h, interconnecting the peripheral part and the boss, the peripheral part 1 being divided into two similar halves by a central gap 1'.

In one end of the piston boss is formed an axial bore 1' the diameter of which is small as compared with the external diameter of the piston. This bore forms part of a fluid operable means for actuating the piston. The other "ice part of the said means comprises a plug k which at one end occupies the said bore and which at its other end is secured to the adjacent cover piece. Also the closed end of the said bore communicates by way of a passage m in the piston web with the portion of the piston which lies opposite the inlet port. In addition a single or duplex spring n is provided between the other end of the piston and the other cover piece c.

To enable the valve to control a reversible flow of motive fluid, a second fluid operable means similar to that above described is provided at the opposite end of the piston, and a second spring is also provided at the end of the piston remote from the second fluid operable means, the corresponding parts being identified by the reference letters j k m and n The arrangement is such that so long as the pressure of the motive fluid supplied to the inlet d is below a given amount, which is determined by the spring n acting on the piston, the piston remains in its central position in which it isolates the outlet port from the inlet port. But when the pressure exceeds that amount, the first described fluid operable means comes into action, causing the piston to be moved in the direction for establishing communication between the inlet and outlet ports. In this condition the liquid flows from the inlet through the interior of the piston and thence through the gap i to the outlet. The piston is returned by the spring when the normal pressure is resumed.

When the flow of the motive fluid is reversed, the piston is movable by the second fluid operable means above mentioned, the other of such means being ineffective.

To enable the force exerted by the spring r to be adjustable for determining the motive fluid pressure at which the valve becomes operative, the spring is supported by an axially movable abutment 0. This latter comprises a disc having a central boss which is in engagement with a screw thread formed on a plug p which is integral with the plug it and extends through the adjacent cover piece 12, its outer end being adapted to be rotated by a manually-operable implement. A similar provision is also made at the other end of the piston as indicated by the reference letters 0 1 Each disc is held against rotation by a spline connection between it and the associated cover piece.

It will be evident from the foregoing description that relatively light springs, and a small force exerted by the motive fluid suflice to impart the required movements to the piston. Consequently the valve is enabled very conveniently to deal with both high motive fluid pressures and large volumes.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

A fluid pressure relief valve comprising in combination a body part having therein a longitudinal bore, and a pair of laterally arranged ports leading to the bore in the regions of its opposite ends respectively, a hollow piston having an outer peripheral part slidably fitted in said bore to control communication between said ports, an inner part in the form of a central boss, and radial web means connecting said outer peripheral part to said central boss, said outer peripheral part being provided at a central position between its ends with a circumferential gap, and said central boss having therein a pair of coaxial blind bores which extend inwardly from opposite ends of said boss, and a pair of passages which extend from the inner ends of said blind bores through said Web means and outer peripheral part to establish communication between said blind bores and said ports respectively, springs acting on opposite ends of said piston to resist movement of the latter from a position in which it interrupts communication between said ports, and stationary plugs extending into and fitting parts of said blind bores so that fluid admitted under pressure to either of said 10 ports has access through one of said passages to one of said blind bores, and tends to move said piston into a position for establishing communication between said ports.

References Cited in the file of this patent UNITED STATES PATENTS 2,468,079 Kirkham Apr. 26, 1949 2,699,178 Adams Jan. 11, 1955 2,791,966 Moulton May 14, 1957 

